Polymeric coating for container induction innerseal

ABSTRACT

Tamper-resistant inner seals that bond firmly to the lips of lidded and capped glass and plastic containers. The innerseals incorporate a metallic foil having a heat sealable adhesive applied to one surface thereof. The heat-sealable adhesive comprises a parafin wax or blend of paraffin wax and microcrystalline wax, polystyrene or derivative thereof, rosin or derivative thereof, and at least one high molecular weight polymeric material selected from the group consisting of ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/methacrylate copolymers, and ethylene/vinyl acetate/methacrylic acid terpolymers, and blends thereof.

TECHNICAL FIELD

This invention relates to a polymeric composition which can be utilizedto prepare a seal for the opening of a container, such as a bottle,which utilizes a conventional screw cap or snap cap closure. Morespecifically, the polymeric composition can be utilized in conjunctionwith other components to provide a seal over the container opening bymeans of induction heating.

BACKGROUND ART

Containers for the dispensing of consumer products such as medicines,foods, etc. which utilize screw top and snap cap closures, are typicallysealed to prevent tampering with the goods therein prior to ultimatepurchase by the consumer. Over the past few years, and especially in theUnited States, such tampering with goods has occurred, resulting ininjury, often severe, and in some cases, even death. Accordingly, it hasbecome apparent that more effective systems for the sealing of suchcontainers are necessary.

One system which has met with significant commercial success bears thetrademark "Safe-Gard". This system provides a hermetic seal that issuitable for use with ingestible commodities. The seal is particularlyeffective for products which should preferably be kept free fromcontamination, oxidation, and/or moisture.

The seal employed in the "Safe-Gard" system typically comprises in orderfrom top to bottom: a pulp board backing, a wax coating, aluminum foil,and a heat sealable polymeric film coating. These materials aretypically supplied in strip form as a laminated structure, and appliedto a strip form as a laminated structure, and applied to a filledcontainer in conventional fashion during the filling process. Afterbeing capped, the filled container is passed through an electromagneticfield generated by induction heating equipment, which heats the outeredge of the aluminum foil, thereby bringing about the melting of theheat sealable polymeric film coating. After the container is removedfrom the induction field, the heat sealable coating will cool and thefoil will be hermetically sealed to the lip of the container. During theinduction heating step, the wax coating between the foil and pulpboardbacking also melts, destroying the bond therebetween. While the waxremains in a molten state for a short period of time, it is wicked up orabsorbed by the pulpboard backing such that the wax bond is permanentlyweakened. Upon removal of the cap from the container, the pulp backingremains with the cap's inner surface, which contacts and seals the lipof the container after the foil liner has been removed by the consumer.

It has been found that the heat sealable polymeric film coatingpresently utilized in the container industry has a relatively weak bondto containers currently used in high speed container-filling industries,such as the food industry. Furthermore, it has been found that thecommercially available heat sealable polymeric film coatings oradhesives can be ineffective for use with various container materials inthe induction innerseal system. For example, while an adhesive may behighly effective for polyethylene containers, it may be relativelyineffective with other conventional plastic containers, such aspolystyrene or polypropylene. Furthermore, while an adhesive may beeffective for plastic containers, it may be ineffective for glasscontainers. Additionally, most commercially available adhesives usefulin induction innerseal systems are not useful for containers havingmetal caps, because these caps dissipate much of the energy availablefor sealing the adhesive.

It has now been discovered that the polymeric composition of thisinvention, when utilized in an induction-activated innerseal system,will provide a strong, heat-sealed bond on glass containers and mostpopular plastic containers, such as polystyrene, polyethylene,polypropylene, polyvinyl chloride, etc., regardless of whether thecontainer has a plastic cap or a metal cap.

SUMMARY OF THE INVENTION

This invention involves a heat sealable polymeric composition for use inconjunction with other elements to provide an innerseal on the openmouth of containers. The composition comprises from about 5 to about 27percent by weight of a paraffin wax or a blend of paraffin wax andmicrocrystalline wax; from about 3 to about 50 percent by weight ofpolystyrene or derivative thereof; from about 5 to about 45 percent byweight of rosin or derivative thereof; from about 30 to about 65 percentby weight of at least one high molecular weight polymeric materialselected from the group consisting ethylene/acrylic acid copolymers,ethylene/vinyl acetate copolymers, ethylene/methacrylate copolymers, andethylene/vinyl acetate/methacrylic acid terpolymers, and blends thereof.If a blend of paraffin wax and microcrystalline wax is employed, the waxblend should contain no more than about 50% by weight microcrystallinewax, with the melting point of the microcrystalline wax being no morethan about 85° C.

The heat sealable polymeric composition is useful for preparinginnerseals that are bonded by induction heating. These innerseals can beused with both glass and plastic containers, and the polymericcomposition makes it possible to use induction heating with metal capsas well as plastic caps.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the invention will be enhanced by referring to theaccompanying drawing, in which like numbers refer to like parts in theseveral views and in which:

FIG. 1 is a greatly enlarged cross section of the inner seal made inaccordance with the invention;

FIG. 2 is a cross sectional view of a screw-on cap having a circle ofthe product of FIG. 1 bonded to the lower surface of the cap, which ispositioned above a container (only the upper portion of which is shown)prior to installing the cap on the mouth of the container; and

FIG. 3 is similar to FIG. 2 but shows the result of heat sealing themouth of the container and subsequently removing the cap.

FIG. 4 is similar to FIG. 3 but shows the result of using apressure-sensitive adhesive in lieu of the microcrystalline wax layerand a paper backing in lieu of a pulpboard backing.

DETAILED DESCRIPTION

The basic elements of an innerseal system 10 for containers based oninduction heating comprise a pulpboard backing 11, a layer 12 of waxcoated thereover, a metallic foil 13, preferably aluminum, applied overthe wax, and a polymeric film 14 coated over the foil capable ofproviding a heat sealed bond. The pulpboard backing 11, wax layer 12,metallic foil 13, and heat sealable polymeric film 14 are allcoextensive. In addition, there may be other layers of materials, suchas polyethylene terephthalate, polyvinylidene chloride, ethylene/vinylacetate, and the like, interposed between the heat sealable polymericfilm and the metallic foil to heighten particular characteristics, suchas, for example a vapor barrier. Also, there may be a film, e.g., paper,interposed between the heat sealable polymeric film and the metallicfoil to provide for increased adhesion, to increase the ability todetect tampering, to increase web rigidity for ease of handling duringcoating operations, or for other purposes.

In some instances, a pulpboard material may already be included withinthe container cap to conform to irregularities in the container opening.In this instance, the wax layer and the pulpboard backing may beunnecessary. Furthermore, if resealability is unnecessary, as forexample with a snap cap closure, these elements again may be omitted.However, the rigidity of the web is preferably maintained sufficientlyhigh for disc punching, web handling, and related manufacturingoperations.

The basic construction of a web for induction sealing of containerstypically comprises as a first element a paper pulpboard backing 11which need not be greater than about 1500 micrometers thick, and ispreferably between about 125 and about 1000 micrometers thick. Anexample thereof is 875 micrometer white lined pulpboard.

The second element, applied over the pulpboard backing 11, is a waxlayer 12, typically less than about 100 micrometers thick, andpreferably about 25 micrometers thick. An example of a commerciallyavailable wax suitable for the wax layer 12 is B² -175 microcrystallinewax, commercially available from Bareco.

The third element is a metallic foil 13, preferably aluminum. The foil13 need not be greater than about 75 micrometers thick, and preferablyis from about 5 to about 37.5 micrometers thick. An example thereof is1145-0 aluminum foil commercially available from Alcoa.

The fourth element is, of course, the heat sealable polymeric film 14 ofthis invention which need not be greater than about 150 micrometersthick, and is preferably from about 12.5 to about 62.5 micrometersthick.

As discussed earlier, other layers of materials can be added to enhancedesired properties, and if resealability of the container is notnecessary, the pulpboard backing 11 and wax layer 12 are not required.

The first component necessary for preparation of the composition for theheat sealable polymeric film 14 of the invention is paraffin wax. Otherwaxes, such as microcrystalline waxes, can be blended with the paraffinwax. The melting point of the paraffin wax, determined pursuant ASTMD-127, is preferably from about 44° C. to about 72° C. At melting pointslower than about 44° C., the coating formed from the composition maytend to block, while a melting point of greater than about 72° C. mayreduce adhesion. If a microcrystalline wax is blended with the paraffinwax, the melting point of the microcrystalline wax is preferably below85° C. If thc melting point is in excess of 85° C., adhesion may beadversely affected. If a microcrystalline wax/paraffin wax blend isemployed, the concentration of microcrystalline wax should not exceed 50percent by weight of thc wax component. A higher concentration ofmicrocrystalline wax may adversely affect adhesion. The paraffin wax orblend containing paraffin wax should be present at from about 5 percentto about 27 percent by weight of the polymeric composition, and morepreferably between about 7 percent and about 20 percent by weight. Belowabout 5 percent, there is a tendency for blocking, and at greater thanabout 27 percent, adhesion between the heat sealed composition and thecontainer is too low, thereby minimizing the ability to detecttampering. The functions of the paraffin wax are to improve the meltflowability of the polymeric composition during the process of coating,to improve adhesion to bottles, particularly glass, to avoid blocking tothe pulp board backing during storage and shipment, and to improvemachine handling ability of the innerseal system. Because paraffin waxwill melt at 165° F. (74° C.) or lower, and its viscosity is very low atcoating temperatures of 250° to 330° F. (121° C. to 165° C.), itspresence in the polymeric composition helps to improve the efficiency ofthe coating process. Thc lubricating characteristics of paraffin waxalso help reduce or prevent gumming and fouling of the dies employed instamping the innerseals.

Representative examples of commercially available paraffin waxes havingutility herein include P-127, P-137, P-167, P-155 (commerciallyavailable from Sun Oil Company), Shellwax® 200, Shellwax® 270(commercially available from Shell Chemical Co.), paraffin 133/135(commercially available from Quaker State Oil Co.). Representativeexamples of microcrystalline waxes having utility herein include B²-175, B² -185 (commercially available from Bareco), "Multiwax" W-835(commercially available from Witco Chemical Co.)

The second component of the polymeric composition is low molecularweight polystyrene or derivatives thereof. Examples of acceptablederivatives include polymeric materials such as alpha-methyl styrene andvinyl toluene/alpha-methyl styrene. The functions of the polystyrene areto improve adhesion and to reduce blocking. The polystyrene orderivative thereof should have a softening temperature, as determined bythe conventional ring and ball test, of at least about 75° C., andpreferably at least 100° C. At a softening temperature of less thanabout 75° C., the coating formed from the composition may tend to block.

The polystyrene or derivative thereof should be present at from about 3to about 50 percent by weight of the polymeric composition, with fromabout 16 to about 42 percent by weight being preferred. At less thanabout 3 percent, adhesion may be reduced and the composition may not besuitable for glass containers and certain plastic containers, e.g.styrene. At greater than about 50 percent, the adhesive may tend toblock and adhesion is reduced.

Examples of commercially available polystyrene or derivatives thereofinclude the "Piccolastic" series of polystyrene and modified polystyrenecompounds, specific examples being A-75, D-75, E-100, etc. Furtherexamples include the "Kristalex" series of polymeric alpha-methylstyrene, such as 3085, 1120, etc.; the "Piccotex" series of polymcricvinyl toluene/alpha-methyl styrene compounds such as 75, LC, 100, etc.;and the "Piccoflex" series of styrene/acrylonitrile copolymericmaterials such as 100, 110, 120, etc. All of the foregoing polystyrenematerials are manufacturcd by Hercules, Inc.

The third component of the polymeric composition is at least onecopolymer selected from the group consisting of ethylene/acrylic acidcopolymers, ethylene/vinyl acetate copolymers, ethylene/methacrylatecopolymers ethylene/vinyl acetate/methacrylic acid terpolymers,andblends thereof. The functions of this ingredient are to promoteadhesion, to increase the strength and flexibility of the polymericcoating, and to act as a matrix to form a smooth, flexible coatingsurface.

Ethylene/acrylic acid copolymers having utility herein include thosehaving an acrylic acid content of from between about 3 to about 20percent by weight and preferably from about 6 to about 13 percent byweight, and a melt index equal to or greater than about 2.5 grams per 10minutes. Commercially available examples of such materials includeEAA-459, EAA-435, manufactured by Dow Chemical Co.

Ethylene/methacrylate copolymers having utility herein are thosecontaining approximately 80 percent by weight ethylene and approximately20 percent by weight methacrylate, and having a melt index equal to orless than about 600 grams per 10 minutes. A commercially availableexample of such a material is EMA-2205 manufactured by Gulf OilCorporation.

Ethylene/vinyl acetate copolymers having utility herein include thosewherein the vinyl acetate content is from about 8 to about 66 percent byweight, with from about 15 to about 43 percent by weight beingpreferred, and a melt index equal to or greater than about 1.5 grams per10 minutes, and preferably from about 8 to about 600 grams per 10minutes. Examples of commercially available ethylene/vinyl acetatecopolymers include "Elvax" 410, "Elvax" 210, "Elvax" 150, etc.manufactured by E. I. duPont de Nemours, Inc., and "Ultrathene" UE-632,manufactured by U.S. Industrial Chemical.

Ethylene/vinyl acetate/methacrylic acid terpolymers having utilityherein include those wherein the vinyl acetate content is between about24 and about 30 percent by weight, and the melt index thereof beingequal to or less than about 600 grams per 10 minutes with a melt indexfrom about 60 to about 470 grams per 10 minutes being preferred.Examples of commercially available ethylene/vinyl acetate/mcthacrylicacid terpolymers include "Elvax" 4310, "Elvax" 4320, etc., manufacturedby E. I. duPont de Nemours, Inc.

If the melt index of the high molecular weight copolymer is too low,incompatibility of the ingredients may result, causing poor adhesion.Excessive melt indices may reduce the cohesive strength of thecomposition such that the tamper-indicating properties of the coatingmay be unacceptable.

If the vinyl acetate content of the copolymers or terpolymers notedabove is too low, the adhesion of the composition to the overlyingmetallic foil will be reduced, again reducing the tamper indicatingproperties thereof. Excessive vinyl acetate content may tend to causethe coating to block.

The concentration of the high molecular weight copolymer componentshould be from about 30 to about 65 percent by weight of the polymericcomposition with from about 30 to about 60 percent by weight beingpreferred. At less than about 30 percent, the cohesive strength may bereduced below an acceptable level, and at greater than about 65 percent,adhesion is unacceptable.

The fourth component necessary for the polymeric composition includesrosin or derivative thereof, e.g, rosin ester, having a softening pointas measured by the ring and ball method of at least about 70° C.,preferably from about 70° C. to about 105° C. The function of the rosinor its derivative is to improve the adhesion of the polymericcomposition to the surface of the container and to improve the meltflowability of the adhesive during the coating process. If no rosin orrosin derivative is employed, the adhesion of the polymeric compositionis poor and the composition may not adhere to certain containermaterials. If the softening point of the rosin ester is greater than105° C., the degree of adhesion will decrease. The concentration of therosin or its derivative should be from about 5 to about 45 percent byweight with from about 10 to about 21 percent by weight being preferred.Representative examples of commercially available rosin derivativesinclude "Foral" Ax (dehydrogenated rosin), "Foral" 85 (glycerol ester ofhydrogenated rosin), and "Foral" 105 (pentaerythritol ester ofhydrogenated rosin), all of which are manufactured by Hercules, Inc.

A fifth component that can be added to the polymeric composition is achlorinated polyolefin, e.g., chlorinated polyethylene, chlorinatedpolypropylene, chlorinated polybutylene, and mixtures thereof.Chlorinated polyolefin will help increase the adhesion of the polymericcomposition to surfaces made of polypropylene. However, it tends todegrade easily during the hot melt compounding, hot melt coating, andheat sealing process. Accordingly, no more than 18 percent by weight andpreferably, no more than 10 percent by weight chlorinated polyolefinshould be included in the composition when it is employed.Representative examples of commercially available chlorinatedpolyolefins include Eastman® CP-343-1, available from Eastman ChemicalProducts, Inc., and "Hardlen" 13-LP, available from Toyo Kasei KogyoCo., Ltd.

The heat sealable polymeric coating can be compounded by utilizingconventional high pressure steam heated glass-lined or stainless steelkettles or oil heated stainless steel kettles for melting and mixingcomponents.

Application of the polymeric coating 14 to the metallic foil substrate13 can be undertaken by conventional techniques, including extrusion andother hot melt coating techniques. Coating weights of the polymericmaterial should be at least about six grams per square meter.Preferably, the coating weights are from about 19 to about 45 grams pcrsquare meter.

To prepare a web l0 for innerseal applications, a metallic foil 13, orpaper-backed metallic foil 13, is obtained directly from vendors. Ifdesired, a film, e.g. polyester, can be conveniently applied to foil 13via conventional technques, e.g., gravure roll coating. Polyester isresistant to high temperaturcs and provides an excellent vapor barrier,two characteristics frequently requested by packagers. The polymericcomposition 14 of the invention can then be hot melt coated ontometallic foil 13 (or onto the paper or film coating thereon, if present)again using conventional techniques. The remaining surface of metallicfoil 13 can then be roll-coated with microcrystalline wax and cooled.The wax-coated surface can then be placed in contact with thc surface ofa pulpboard sheet and passed through squeeze rolls at elevatedtemperature, thereby laminating foil 13 to pulpboard backing 11 whileleaving heat-sealable layer 14 exposed. The resulting inner sealconstruction can then be slit to suitable widths, from which circulardiscs, corresponding to the inner diameter of screw-on lids, can be diecut.

As is well known in the inner seal art, the combination of the varioussheets and foils in the foregoing embodiment represents only onespecific construction. To illustrate, the foil may be prelaminated to asheet of paper, the pulpboard may be prelaminated to a polyester film,etc.

In an alternative construction, pulpboard backing 11 can be replacedwith a backing 11a made from paper, chipboard, polymeric foam, or thelike, and microcrystalline wax layer 12 can be replaced by a layer 12aof an adhesive, e.g., pressure-sensitive adhesive. This adhesiveexhibits sufficient adhesive strength to permanently bond backing 11a tofoil 13. An example of this construction is shown in FIG. 4.

FIG. 2 shows composite innerseal 10 mounted inside screw-on top 16.After container 20 has been filled cap 16 is screwed into the mouth ofcontainer 20, after which the capped container is passed through a radiofrequency field, the resulting eddy currents inductively heating metalfoil 13 and simultaneously melting wax layer 12 and heat-sealableadhesive layer 14. As wax 12 melts, it is absorbed by pulpboard backing11, greatly weakening the bond between backing 11 and metal foil 13. Asthe capped container cools to room temperature, heat-sealable adhesive14 bonds firmly to the lip of container 20. When cap 16 is subsequentlyunscrewed from container 20, pulpboard backing 11 twists free from foil13, which remains firmly bonded to the lip of container 20 by means ofheat-sealable adhesive 14, whereby providing a tight seal which preventsleakage. Because foil 13 tears when subjected to peeling forces, it alsoprovides an indication that tampering may have occurred.

The heat sealable polymeric film coating of this invention provides astronger bond to containers than do conventional heat sealable polymericfilm coatings. The polymeric film is also universally effective in thatit is useful in innerseals for both glass and plastic containers.Furthermore, the polymeric film is useful for induction innersealsystems using either plastic caps or metal caps. Even though metal capsdissipate much of the energy available for sealing the polymeric film tothe lip of the container, the heat scalable polymeric film of thisinvention provides sufficient adhesive strength to render it useful forinduction innerseal systems employing these caps.

The invention will now be more fully described by the followingnon-limiting examples, wherein all parts are by weight unless otherwisespecified.

ln each example, the innerseal comprised (1) an 875 micrometer whiteline pulpboard backing, (2) a layer of microcrystalline wax having athickness of about 25 micrometers, (3) an aluminum foil (Alcoa 1145-0)having a thickness of 1 mil, and (4) a heat sealable polymeric filmcontaining paraffin wax, rosin derivative, polystyrene, and ethylenecopolymer. In the primary examples, the concentration of each ingredientin the heat sealable polymeric film was within the acceptable ranges. Inthe comparative examples, the concentration of some of the ingredientsin the heat sealable composition was outside of the acceptable ranges.

In each example, a determination of the adhesion characteristics tospecific containers is made by manual testing, i.e., the foil isattempted to be hand peeled from the edges of the container openingwhere the seal should be effective.

EXAMPLES 1-2

To a glass jar was first added the paraffin wax or wax blend. Thetemperature of the composition in thc jar was maintained between 280° F.and 320° F. As the wax was melting, the polystyrene derivative was addedto the jar, followed by the rosin derivative, and then the ethylenecopolymer. During the addition of the ingredients, the contents of thejar were stirred so that the resulting composition would be homogeneous.The following table sets forth the ingredients, trade names, and amountsthereof for each working example (1,2) and for five comparative examples(A, B, C, D, E). All amounts are in parts by weight.

                                      TABLE I                                     __________________________________________________________________________                      Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                     Ingredient  1  2  A      B      C      D      E                               __________________________________________________________________________    Paraffin Wax                                                                              14.3                                                                             10.0                                                                             12.6          14.3   40.0                                   P-137                                                                         Microcrystalline wax                                                          Multiwax W-835  4.3                                                           B.sup.2 -175             14.3                                                 Polystyrene                                                                   Kristalex 1120                                                                            28.6   6.3   28.6   28.6   10.0   33.3                            Kristalex 3100 28.6                                                           Rosin derivative                                                              Foral AX    14.3   6.3   14.3           7.1   16.6                            Foral 85       14.3                                                           Polyterpene derivative          14.3                                          Zonarez B-70.sup.1                                                            Ethylene copolymer                                                            Elvax 4320  42.8  75.0   42.8                                                 Elvax 310      42.8                                                           Elvax 4355                      42.8                                          Elvax 4310                             35.7                                   EAA 409                                 7.2                                   Elvax 260                                     50.0                            __________________________________________________________________________     .sup.1 Zonarez B70 is commercially available from Arizona Chemical            Company.                                                                 

Each heat-sealable adhesive composition was then hot melt coated on oneface of 25-micrometer aluminum foil in an amount equal to approximately30 g/m².

As is conventional, the other face of the aluminum foil was then rollcoated with molten (95° C.) microcrystalline wax and cooled, leaving acoating weight of about 7.5 mg/in². The wax-coated surface was thenplaced in contact with the surface of a pulpboard sheet and passedthrough squeeze rolls at a temperature of 55° C., thereby laminating thealuminum foil to the pulpboard while leaving the heat-sealable adhesivelayer exposed. The innerseal was then tested for blocking. To pass theblocking test, no adhesive can transfer to the pulpboard backing and nopulpboard fiber can transfer to the adhesive when the adhesive is placedin contact with the pulpboard backing. The resultant inner sealconstruction was then slit to suitable widths, from which circulardiscs, corresponding to the inner diameter of screw-on lids, weredie-cut. A suitable adhesive was then employed, in conventional manner,to bond the pulpboard face of one of these discs to the inner surface ofthe screw-on cap for a glass jar.

The lid was screwed onto a glass jar using appropriate torque; forexample, with a glass jar having a 38-mm inside diameter. The jar wasthen passed through a radio frequency field adjacent the lid for about0.7-1.0 second, which was sufficient to bond the aluminum foil to thelip, simultaneously melting the microcrystalline wax, which diffusedinto the pulpboard and weakened the bond between the foil and thepulpboard. The sealed jar was then cooled to room temperature. The sealswere then tested for tamper-indicating ability. To pass thetamper-indicating test, at least 50% of the innerseal material mustremain on the lip of the jar when the cap is unscrewed. Theheat-sealable compositions of Examples 1 and 2 passcd both tests. Thecompositions of Comparative Examples A, B, C and D failed thetamper-indicating test. The composition of Comparative Example E failedthe blocking test.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. An article suitable for preparing a containerinnerseal comprising a pulpboard backing, a layer of wax coated oversaid backing, metallic foil overlying said wax layer, and a layer of apolymeric composition consisting essentially of from about 5 to about 27percent by weight of-paraffin wax or blend of paraffin wax andmicrocrystalline wax, from about 3 to about 50 percent by weight ofpolystyrene or derivative thereof having a softening temperature of atleast about 75° C., from about 5 to about 45 percent by weight of rosinor derivative thereof havinq a softening temperature of at least about70° C., and from about 30 to about 65 percent by weight of at least onehigh molecular weight polymeric material selected from the groupconsisting of ethylene/acrylic acid copolymers having an acrylic acidcontent of from about 3 to about 20 percent by weight and a melt indexequal to or greater than about 2.5 grams per 10 minutes, ethylene/vinylacetate copolymers having a vinyl acetate content of from about 8 toabout 66 percent by weight and a melt index equal to or greater thanabout 1.5 grams per 10 minutes, ethylene/methacrylate copolymerscontaininq approximately 80 percent by weight ethylene and approximately20 percent by weight methacrylate and having a melt index equal to orless than about 600 grams per 10 minutes, and ethylcne/vinylacetate/methacrylic acid terpolymers having a vinyl acetate contentbetween about 24 and about 30 percent by weight and melt index beingequal to or less than about 600 grams per 10 minutes coated over saidmetallic foil.
 2. The article of claim 1 wherein the metallic foilcomprises aluminum.
 3. The article of claim 1 wherein the layer of waxcoatcd over said backing comprises microcrystalline wax.
 4. A containerinnerseal comprising a pulpboard backing, a layer of wax coated oversaid backing, metallic foil overlying said wax layer, and a polymericlayer coated over said metallic foil, said polymeric layer formed from apolymeric composition consisting essentially of from about 5 to about 27percent by weight of paraffin wax or blend of paraffin wax andmicrocrystalline wax, from about 3 to about 50 percent by weight ofpolystyrene or derivative thereof having a softening temperature of atleast about 75° C., from about 5 to about 45 percent by weight of rosinor derivative thereof having a softening temperature of at least about70° C., and from about 30 to about 65 percent by weight of at least onehigh molecular weight polymeric material selected from the groupconsisting of ethylene/acrylic acid copolymers having an acrylic acidcontent of from about 3 to about 20 percent by weight and a melt indexequal to or greater than about 2.5 grams per 10 minutes, ethylene/vinylacetate copolymers having a vinyl acetate content of from about 8 toabout 66 percent by weight and a melt index equal to or greater thanabout 1.5 grams per 10 minutes, ethylene/methacrylate copolymerscontaining approximtely 80 percent by weight ethylene and approximately20 percent by weight methacrylate and having a melt index equal to orless than about 600 grams per 10 minutes, and ethylene/vinylacetate/methacrylic acid terpolymers having a vinyl acetate contentbetween about 24 and about 30 percent by weight and melt index beingequal to or less than about 600 grams per 10 minutes.
 5. A containercomprising the innerseal of claim
 4. 6. The article of claim 4 whereinthe metallic foil comprises aluminum.
 7. The article of claim 4 whereinthe layer of wax coated over said backing comprises microcrystallinewax.
 8. An article suitable for preparing a container innersealcomprising a backing, a layer of adhesive coated over said backing,metallic foil overlying said adhesive layer, and a layer of a polymericcomposition consisting essentially of from about 5 to about 27 percentby weight of paraffin wax or blend of paraffin wax and microcrystallinewax, from about 3 to about 50 percent by weight of polystyrene orderivative thereof having a softening temperature of at least about 75°C., from about 5 to about 45 percent by weight of rosin or derivativethereof having a softening temperature of at least about 70° C., andfrom about 30 to about 65 percent by weight of at least one highmolecular weight polymeric material selected from the group consistingof ethylene/acrylic acid copolymers having an acrylic acid content offrom about 3 to about 20 percent by weight and a melt index equal to orgreater than about 2.5 grams per 10 minutes, ethylene/vinyl acetatecopolymers having a vinyl acetate content of from about 8 to about 66percent by weight and a melt index equal to or greater than about 1.5grams per 10 minutes, ethylene/methacrylate copolymers containingapproximately 80 percent by weight ethylene and approximately 20 percentby weight methacrylate and having a melt index equal to or less thanabout 600 grams per 10 minutes, and ethylene/vinyl acetate/methacrylicacid terpolymers having a vinyl acetate content between about 24 andabout 30 percent by weight and melt index being equal to or less thanabout 600 grams per 10 coated over said metallic foil.
 9. The article ofclaim 8 wherein the metallic foil comprises aluminum.
 10. A containerinnerseal comprising a backing, a layer of adhesive coated over saidbacking, metallic foil overlying said adhesive layer, and a polymericlayer coated over said metallic foil, said polymeric layer formed from apolymeric composition consisting essentially of from about 5 to about 27percent by weight of paraffin wax or blend of paraffin wax andmicrocrystalline wax, from about 3 to about 50 percent by weight ofpolystyrene or derivative thereof having a softening temperature of atleast about 75° C., from about 5 to about 45 percent by weight of rosinor derivative thereof having a softening temperature of at least about70° C., and from about 30 to about 65 percent by weiqht of at least onehigh molecular weight polymeric material selected from the groupconsisting of ethylene/acrylic acid copolymers having an acrylic acidcontent of from about 3 to about 20 percent by weight and a melt indexequal to or greater than about 2.5 grams per 10 minutes, ethylene/vinylacetate copolymers having a vinyl acetate content of from about 8 toabout 66 percent by weight and a melt index equal to or greater thanabout 1.5 grams per 10 minutes, ethylene/methacrylate copolymerscontaining approximately 80 percent by weight ethylene and approximately20 percent by weight methacrylate and having a melt index equal to orless than about 600 grams per 10 minutes, and ethylene/vinylacetate/methacrylic acid terpolymers having a vinyl acetate contentbetween about 24 and about 30 percent by weight and melt index beingequal to or less than about 600 grams per 10 minutes.
 11. The article ofclaim 10 wherein the metallic foil comprises aluminum.
 12. A containercomprising the innerseal of claim 10.